An adhesive dressing is typically composed of an adhesive which is coated on a backing layer and the dressing is typically further provided with an absorbent layer e.g. in the form of an absorbent pad. Such an adhesive dressing should have adhesion suitable for firmly adhering the dressing to the skin and subsequently easily removing it from the skin. Furthermore, the dressing should have high water vapour permeability to avoid skin damage because it is directly attached to the skin, in which high water vapour permeability can promote wound healing.
Conventionally, the adhesive of dressings has the pressure-sensitive adhesive coated onto an entire surface of the backing layer. Thus, conventional dressings are disadvantageous in terms of low water vapour permeability, due to the coated adhesive per se, regardless of the water vapour permeability of the backing layer. That is, even though a backing layer having high water vapour permeability is used, the adhesive coated on the entire surface of the backing layer may prevent water vapour permeation, whereby the water vapour permeability of the dressing is reduced.
Wound dressings comprising soft adhesives, such as for example silicone, polyurethane or acrylate based adhesives are popular due to their softness. These soft adhesives are often solvent based and manufacturing dressings with these usually includes a drying or curing step and limited opportunity of modelling the adhesive after these steps.
Most of the known coating methods with such adhesives can only coat one uniform thickness at one time and the amount of waste in the process may be substantial.
If the absorbent pad is directly attached to the middle of the coated backing layer, the adhesive area between the absorbent pad and backing layer is largely wasted as it is not used for adhesion to the skin as intended. The adhesive, though formulated for good properties for skin contact, may not have the optimal properties for attaching the absorbent pad. For attachment of the absorbent pad, a cheaper or more effective adhesive or attachment method may be used.
An exposed absorbent pad on a backing layer requires good anchorage to the backing layer, especially when wet and heavy due to being soaked with exudate. By good anchorage is meant that absorption of moisture does not cause the absorbent pad and the backing layer to delaminate.
An exposed absorbent pad surface facing the wound side maximises the exudate absorption when in place. However, longer term placement (such as for a period longer than 3-5 days) on the wound may lead to ingrowth of tissue of the healing wound onto the absorbent core surface or more difficult removal, which in turn irritates the wound.
To overcome the removal problem, contact layers of less adhering nature are known. These contact layers are often thin films or gel layers having perforations to expose the absorbent core.
Another function of the contact layer may be to support and hold the absorbent core in position.
There is a need to simplify and improve the processes of dressing construction with different patterns and thicknesses of the different parts of the adhesive layer. There is a need to maximize the contact area to skin but minimize the coverage of the backing film.